Rock Bolt

ABSTRACT

A rock bolt well adapted for use in mining is provided. The rock bolt includes an anchor tube that encloses an interior space, a fixing agent arranged inside the interior space for the substance-to-substance fixation of the anchor tube to stone, a mobile piston arranged inside the interior space for transporting the fixing agent out of the anchor tube when the anchor tube is arranged in a bore hole in the stone, a piston moving mechanism, an anchor nut, and an anchor plate supported by the anchor nut for support on the stone.

RELATED APPLICATIONS

The present application claims priority to German Patent Application DE10 2010 063 098.5, filed Dec. 15, 2010, and entitled “Gesteinsanker”(“Rock Bolt”), the entire content of which is incorporated herein byreference.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[Not Applicable]

[MICROFICHE/COPYRIGHT REFERENCE]

[Not Applicable]

BACKGROUND OF THE INVENTION

The present invention relates to a rock bolt, for example, for miningapplications, and a method for fixing a rock bolt in stone.

In mining and tunnel construction rock bolts are used in order toprevent rock movements of adjacent stone, to slow such movements, or tosecure larger split-offs of adjacent rock, and thus allow a saferoperation. Here, two functional principles are known, which sometimesare combined. In mechanical systems the fastening of the anchor occursby friction fitting, with mechanical stone and/or rock anchors generallyalso showing an expanding sleeve. In chemical rock bolts the anchortubes are connected to a curing cement or resin as a fixation means in asubstance-to-substance manner to the base and/or the adjacent stone. Therock bolts are installed here with or without any prestressing in theadjacent stone. Contrary to tunnel construction, rock bolts in mining,e.g., underground coal mining, serve only for a temporary securing ofthe stone, because generally the temporarily secured stone will be minedin a later processing step and thus the rock bolts are removed againfrom the stone.

U.S. Pat. No. 4,601,614 shows a rock bolt for tunnel construction andmining. A two-component fixing agent in two cartridges is arrangedinside an interior space enclosed by an anchor tube. The external end ofthe anchor tube comprises an opening to introduce water under highpressure into the interior space enclosed by the anchor tube. A pistonis arranged articulate inside the interior space and by moving thepiston the two-component fixing agent is transported and/or pressedthrough holes in the anchor tube into a space between the anchor tubeand the stone. For this purpose, an opening is provided at the externalend of the anchor tube, through which water can be introduced under highpressure into the interior space enclosed by the anchor tube and by thiswater the piston is pressurized, so that the piston is moved inwardlyand thus the fixation means is expressed. It is thereforedisadvantageously necessary to require a high pressure pump to createhighly pressurized water to move the piston for a substance-to-substancefastening of the anchor tube with the fixing agent.

BRIEF SUMMARY OF THE INVENTION

An objective of aspects of the present invention therefore comprisesproviding a rock bolt and a method for fixing a rock bolt in stone, inwhich with little technical expense the fixing agent can be insertedinto the space between the stone and the anchor tube and/or the rockbolt embodied as a gliding anchor requires only little space in thetunnel and/or work gallery produced underground.

Such an objective may be attained in a chemical rock bolt, particularlyfor application in mining, comprising an anchor tube, which encloses aninterior space, a fixing agent arranged inside the interior space for asubstance-to-substance fixation of the anchor tube at the stone, amobile piston arranged inside the interior space to transport the fixingagent out of the anchor tube when arranging the anchor tube in a borehole in the stone, at least one means to move the piston, an anchor nut,and an anchor plate supported by the anchor nut to be placed upon thestone. The at least one means may be embodied as a spindle drive formoving the piston and/or the anchor nut and the anchor plate fastened ata rod arranged inside the anchor tube. The rod may be fastened at theanchor tube with a fastening device such that the fastening of the rodat the anchor tube is only released when a predetermined tensile forcein the rod is exceeded, and thus the rod is partially mobile towards theoutside such that the rock bolt represents a gliding anchor. The anchornut and the anchor plate can be embodied as a single piece or as twoseparate components.

In order to move the piston, i.e., to express the fixing agent out ofthe interior space into a space between the anchor tube and the stone,it is therefore no longer required to expensively provide ahigh-pressure pump in the tunnel or gallery in order to move the pistonwith high-pressurized water. The rock bolt comprises a spindle drive sothat the piston can be moved by a mere application of a torque at therock bolt, particularly at the outside.

The rock bolt may also be further embodied as a gliding anchor. Thegliding anchor shows a gliding function such that beginning at apredetermined tensile force compensated by the rock bolt, i.e., at thepressure acting upon the anchor plate which is caused by the stone, therock bolt is extended in its length and thus a motion is permitted atthe stone which reduces the tensile forces compensated at the rod (belowthe predetermined tensile force as a threshold, so that no more glidingoccurs) and thus a better securing of the stone is ensured. Here, afterthe expression of the fixing agent from the interior space the rod isessentially arranged underneath the interior space, i.e., the rodprojects only slightly beyond the exterior end of the anchor tube, sothat the gliding anchor requires only little structural space outsidethe stone. In the gliding anchors known from prior art the glidingfunction at the anchor nut is implemented such that the anchor nutglides outwardly at a larger projection of the rod and/or the anchortube. Thus, in the gliding anchors known from prior art a large amountof space is required prior to the gliding of the gliding anchor for theprojection at the anchor tube and/or the rod for the nut.

According to aspects of the present invention, if the tensile force tobe compensated by the rod and/or the force at the rock bolt to becompensated by the rod at the fastening device falls below apredetermined tensile force the motion of the rod towards the outside ishindered again, relative to the anchor tube with the fastening device,so that greater forces can be compensated by the rock bolt.

In an additional embodiment, the rod represents a threaded rod with anexternal thread and the fastening device is an annular part with aninternal thread, e.g., a nut, and the annular part is fastened at theanchor tube and the internal thread of the annular part engages theexternal thread of the threaded rod.

In an additional embodiment, the annular part is embodied in one pieceat the anchor tube, particularly by an internal thread being embodiedinside the anchor tube. The annular part can here represent a separatepart fastened to the anchor tube or an annular part with an internalthread can be embodied in one piece with the anchor tube, for example,such that an internal thread is provided at the external end sectioninside the anchor tube.

In another variant the internal thread of the annular part is embodiedas a specialty thread, which destroys the external thread of thethreaded rod only beginning at a predetermined tensile force or viceversa.

Beneficially, the spindle drive to move the piston may be formed fromthe threaded rod and the annular part with the internal thread.

In an additional embodiment, the piston is fastened directly orindirectly at the threaded rod.

In an additional embodiment, the rear end of the anchor tube is closedby a cap, and the anchor tube and/or the cap comprise at least oneopening to guide the fixing agent out of the interior space enclosed bythe anchor tube. On the one hand, the cap can be a separate part, oralso be embodied in one piece together with the anchor tube.

In a supplementary embodiment, the fixing agent, particularly resin orcement, comprises two components, e.g., an adhesive component and acuring component.

Preferably the two components are each arranged separated in a bag.Here, any device for storing the two separate components is considered abag, for example a cartridge or any other container.

In an amended embodiment a mixer is arranged between the fixing agentand at least one opening to mix the fixing agent, particularly the twocomponents, before the fixing agent is ejected through at least oneopening.

Beneficially, the rod may be provided with a stop, preferably an annularstop, so that the mobility of the rod towards the outside is limited bysaid stop. Here, the stop may be a separate component or be embodied inone piece with the rod, particularly a threaded rod. Furthermore, thestop may also be formed by the piston.

A method according to aspects of the present invention for fixing a rockbolt in stone, particularly a rock bolt as described in thisapplication, includes the steps of implementing a bore hole in thestone, inserting the rock bolt into the bore hole, transporting a fixingagent from an interior space enclosed by an anchor tube of the rock boltthrough at least one hole into a space, particularly an annular spacebetween the anchor tube and the stone, by way of moving a piston in theinterior space towards a fixing agent, a substance-to-substancefastening of the anchor tube by the fixing agent to the stone, andcuring the fixing agent, with the piston being moved by a spindle driveat the rock bolt, particularly inside an interior chamber enclosed bythe anchor tube.

In an additional embodiment the spindle drive comprises a threaded rod.A torque is applied from the outside to the threaded rod such that thethreaded rod is set into a rotary motion about the longitudinal axis ofthe threaded rod, and the threaded rod is screwed with an externalthread to an internal thread at the anchor tube such that the threadedrod performs an axial motion towards the inside, i.e., the threaded rodis screwed into the interior space enclosed by the anchor tube.

In an additional variant the piston fastened at the threaded rodperforms the inwardly directed axial motion together with the threadedrod.

In an additional variant, prior to the threaded rod being screwed intothe interior space enclosed by the anchor tube, the threaded rod is onlypartially arranged in the interior space enclosed by the anchor tube,and during the expression of the fixing agent from the interior spaceenclosed by the anchor tube the threaded rod is essentially entirelyscrewed into the interior space enclosed by the anchor tube. Here,“essentially entirely screwed into the interior space enclosed by theanchor tube” means that the threaded rod is screwed into the interiorspace, for example, by at least about 70%, 80%, 90% or 95%. This way,only a small part of the threaded rod, i.e., for example, less thanabout 30%, 20%, 10%, or 5% is arranged outside the interior space sothat after the screwing in and the compression of the space between theanchor tube and the stone with the fixing agent the rock bolt requiresonly little operating space in the tunnel or gallery.

In an additional embodiment the components of the rock bolt, for examplethe anchor tube, the piston, the spindle drive, the anchor nut, theanchor plate, the rod, the fastening device, the annular part, the cap,and/or the stop are made at least partially, preferably entirely, frommetal, for example steel or a steel alloy, or fiberglass-reinforcedplastic.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

In the following an exemplary embodiment of the invention is describedin greater detail with reference to the attached drawings.

FIG. 1 shows a longitudinal cross section of a rock bolt formed inaccordance with an embodiment of the present invention, which isinserted into a bore hole in stone with a fixing agent not yet insertedinto the space between the stone and the anchor tube.

FIG. 2 shows a longitudinal cross section of the rock bolt according toFIG. 1, in which the fixing agent is inserted into the space between thestone and the anchor tube.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with an embodiment of the present invention, a rock bolt 1embodied as a gliding anchor 2 may be used in mining for the temporarysecuring of stone in galleries. The rock bolt 1 comprises an anchor tube3, which encloses an interior space 4. The rock bolt 1 represents achemical rock bolt 1, i.e., using a fixing agent 5 arranged in theinterior space 4 to the anchor tube 3 to be fastened in asubstance-to-substance fashion to the stone 28. For this purpose, a borehole 29 must be implemented in the stone 28 and then the rock bolt 1must be inserted into the bore hole 29. This status is shown in FIG. 1,prior to the expression of the fixing agent 5 into a space between theanchor tube 3 and the stone 28. FIG. 2 shows the rock bolt 1 connectedto the stone 28 in a substance-to-substance manner. In the illustratedembodiment, the fixing agent 5 represents a resin 6, which includes anadhesive component 7 and a curing component 8. The adhesive component 7is stored in a first bag 9 and the curing component 8 is stored in asecond bag 10. The two bags 9, 10 are stored in the interior space 4.

Prior to the expression of the fixing agent from the interior space 4, arod 16, embodied as a threaded rod 17 in the illustrated embodiment, isarranged approximately half in the interior space 4, with the other halfoutside the interior space 4, i.e., in an operating space 30 of a hollowspace or gallery for mining. A fastening device 19 is fixed inside atthe anchor tube 3 in the exterior end section as an annular part 20 atthe anchor tube 3. The annular part 20, for example, a nut 21 with aninternal thread 22, is, in the illustrated embodiment, for example,welded to the anchor tube 3. Here the external thread 18 of the threadedrod 17 engages the internal thread 22 of the annular part 20 so thatthis way the threaded rod 17 is indirectly fastened to the anchor tube3. A piston 11 is fastened at the interior end of the threaded rod 17.The interior end of the anchor tube 3 is closed by a cap 23 with anopening 24. Through the opening 24, the fixing agent 5 can flow from theinterior space 4 of the anchor tube 3 towards the outside into thespace, particularly annular space, between the anchor tube 3 and thestone 28. In the illustrated embodiment, a mixer 25 is arranged at theopening 24, through which, due to the geometric arrangement of the mixer25 in the interior space 4, the fixing agent 5 must mandatorily flowfrom the two bags 9, 10 first through the mixer 25 and then through theopening 24 to the outside. Here, the mixer 25 comprises, for example anappropriate geometry, such that the fixing agent 5 flows meanderingly ortube-like through the mixer 25 and thus a mixing of the adhesivecomponent 7 with the curing component 8 of the resin 6 occurs prior toflowing out of the opening 24.

At the exterior outer end of the threaded bolt 17 an anchor nut 14 isscrewed onto the external thread 18 of the threaded rod 17 with aninternal thread and an anchor plate 15 is placed on the anchor nut 14.In the illustrated embodiment, the anchor plate 15 comprises a bore holewithout an internal thread, with the threaded rod 17 being arrangedtherein. Thus, according to the illustration in FIG. 2, a pressure canbe applied by the stone 28 upon the anchor plate 15. This pressure istransferred from the anchor plate 15 to the anchor nut 14 and from theanchor nut 14 to the threaded rod 17 so that a tensile force is appliedto the threaded rod 17. This tensile force is transferred via theannular part 20 to the anchor tube 3 and from the anchor tube 3 at theoutside in a substance-to-substance manner (by a substance-to-substancecontact) by the fixing agent 5 to the stone 28.

The piston 11 is moved inwardly in order to insert the fixing agent 5into the space between the anchor tube 3 and the stone 28, i.e.,according to the illustration of FIG. 1, upwardly. This way, the piston11 destroys the first and second bag 9, 10 so that the adhesivecomponent 7 and the curing component 8 move, and due to the reducingvolume of the internal space 4 between the piston 11 and the cap 23, thefixing agent 5 is pressed through the mixer 25 and the opening 24 intothe space between the anchor tube 4 and the stone 28, and subsequentlycures. For this purpose, the rock bolt 1 comprises a spindle drive 13 asa mechanism 12 configured to move the piston 11. Here, the threaded rod17 and the annular part 20 with the internal thread 22 serve as thespindle drive 13. The external end of the threaded rod 17 includes arespective geometry, for example the shape of a hexagon in the crosssection, so that a torque can be applied upon the threaded rod 17, forexample via a pneumatic screw, and thus the threaded rod 17 is set intoa rotary motion about its longitudinal axis. This way, the threaded rod17 is moved inwardly, i.e., according to the illustration in FIG. 1,towards the top, due to the engagement of the external thread 18 of thethreaded rod 17 with the internal thread 22 of the annular part 20.

With the motion of the threaded rod 17 the piston 11 also performs themotion according to the illustration of FIG. 1 upwards, because thepiston 11 is fastened to the threaded rod 17. In FIG. 2 the fixing agent5 is already pressed into the space between the anchor tube 3 and thestone 28, i.e., the anchor tube 3 is fastened to the stone 28 in asubstance-to-substance fashion, particularly by way of gluing. Here, inthe installed state shown in FIG. 2, the threaded rod 17 is essentiallycompletely arranged inside the interior space 4. Thus, only a smallportion of the threaded rod 17, for example less than about 10% or 5%,is located outside the interior space 4. This way, in the installedstate of the rock bolt 1 only very little operating space is required inthe operating area 30 in the mining gallery. In the installed stateaccording to FIG. 2 the anchor plate 15 contacts the stone 28 and thuscan compensate pressures. Further, shear forces perpendicular inreference to a longitudinal axis of the threaded rod 17 and/or theanchor tube 3 can also be compensated by the rock bolt 1 and thus thestone 28 can additionally be secured.

In the illustrated embodiment, the rock bolt 1 is embodied as a glidinganchor 2. For this purpose, the internal thread 22 of the annular part20 is embodied as a specialty thread, which beginning at a predeterminedtensile force in the threaded rod 17 destroys the external thread 18 ofthe threaded rod 17, for example, by way of shearing, so that in thisway the threaded rod 17 is moved outwardly, i.e., according to theillustration in FIG. 2, downwards in reference to the anchor tube 3.Here, the anchor nut 14 as well as the anchor plate 15 move togetherwith the threaded rod 17 outwardly. This way, movements of the stone 28can be compensated by the rock bolt 1 being a gliding anchor 2 withoutthis leading to the rock bolt 1 breaking. When the tensile force and/orthe pressure to be compensated by the threaded rod 17 upon the anchorplate 15 falls back below the predetermined threshold for the tensileforce, the external thread 18 of the threaded rod 17 is no longerdestroyed by the specialty thread of the internal thread 22 of theannular part 20, and the threaded rod 17 no longer moves towards theoutside.

A stop 26 embodied as an annular stop 27 in the upper end section of thethreaded rod 17 provides that during gliding, i.e. during a motion ofthe threaded rod 17 towards the outside, the rod cannot completely moveout. By the annular stop 27 contacting the annular part 20 a gliding ofthe gliding anchor 2 and/or a motion of the threaded rod 17 towards theoutside is prevented. After the annular stop 27 has contacted theannular part 20, the gliding anchor 2 is no longer able to glide andcompensates the tensile forces at the threaded rod 17 until the tensileforces applied cause the rock bolt 18 to fail, for example the threadedbolt 17 breaking or the adhesive bonding failing between the fixingagent 5 and the stone 28.

Overall, the rock bolt described above provides valuable advantages. Inorder to move the piston 11, i.e. the expression of the fixing agent 5from the interior space 4, provision of expensive high-pressure pumps isno longer required in mining operations. The piston 11 can be moved byonly applying a torque upon the threaded rod 17 at the outside, forexample via a pneumatic screw. In the installed state according to FIG.2, the rock bolt 1 only requires little operating space 30, because thethreaded rod 17 is arranged only slightly outside the anchor tube 3 toaccept the anchor nut 4 and the anchor plate 15, and shows no increasedlength outside the interior space 4 in the installed state according toFIG. 2 to compensate gliding motions of the anchor nut 14 on thethreaded rod 17.

1. A rock bolt comprising: an anchor tube that encloses an interiorspace; a fixing agent initially arranged inside the interior space ofthe anchor tube, the fixing agent configured to provide asubstance-to-substance fixation of the anchor tube to stone into whichthe anchor tube is inserted, a mobile piston arranged inside theinterior space of the anchor tube, the mobile piston configured totransport the fixing agent out of the anchor tube; an anchor nut; ananchor plate supported by the anchor nut, the anchor plate configured tosupport the stone into which the rock bolt is inserted; and a pistonmoving mechanism configured to move the mobile piston, the piston movingmechanism comprising a spindle drive.
 2. A rock bolt according to claim1 wherein the anchor nut and the anchor plate are fastened at a rodarranged inside the anchor tube, the rod being fastened via a fasteningdevice at the anchor tube such that the fastening of the rod at theanchor tube is only released beginning at a predetermined tensile forcein the rod, whereby the rod can be partially moved outwardly so that therock bolt comprises a gliding anchor.
 3. A rock bolt according to claim1, comprising a threaded rod and a fastening device, the threaded rodcomprising an external thread, the fastening device comprising anannular part with an internal thread, wherein the annular part isfastened at the anchor tube and the internal thread of the annular partengages the external thread of the threaded rod.
 4. A rock boltaccording to claim 3, wherein the internal thread of the annular part islocated inside of the anchor tube.
 5. A rock bolt according to claim 3,wherein the internal thread of the annular part comprises a specialtythread which destroys the external thread of the threaded rod beginningat a predetermined tensile force.
 6. A rock bolt according to claim 1,wherein the spindle drive comprises a threaded rod and an annular partwith an internal thread, the internal thread engaging the threaded rod.7. A rock bolt according to claim 6, wherein the mobile piston isfastened directly or indirectly to the threaded rod.
 8. A rock boltaccording to claim 1, wherein a rear end of the anchor tube is closed bya cap, and at least one of the anchor tube and the cap comprises atleast one opening to guide the fixing agent from the interior spaceenclosed by the anchor tube.
 9. A rock bolt according to claim 1,wherein the fixing agent comprises an adhesive component and a curingcomponent.
 10. A rock bolt according to claim 9, wherein the adhesiveand curing components are each arranged in separate bags.
 11. A rockbolt according to claim 1, wherein a mixer is arranged between thefixing agent and at least one opening of the anchor tube, the mixerconfigured to mix the fixing agent prior to the emission of the fixingagent from at least one opening.
 12. A rock bolt according to claim 5wherein the threaded rod comprises a stop positioned and configured tolimit the ability of the threaded rod to move outwardly.
 13. A methodfor fixing a rock bolt comprising the steps of: implementing a bore holeinto stone; inserting the rock bolt into the bore hole; transporting afixing agent from an interior space enclosed by an anchor tube of therock bolt through at least one opening into a space between the anchortube and the stone by moving a piston in the interior space towards thefixing agent, wherein the piston is moved via a spindle drive of therock bolt; fastening of the anchor tube to the stone with the fixingagent; and, allowing the fixing agent to cure.
 14. A method according toclaim 13, wherein the spindle drive comprises a threaded rod, andwherein moving the piston comprises applying a torque upon the threadedrod from the outside such that the threaded rod is set into a rotarymotion about a longitudinal axis of the threaded rod and the threadedrod is screwed with an external thread to an internal thread proximateto the anchor tube so that by the threaded rod an axial motion isperformed inwardly such that the threaded rod is screwed into theinterior space enclosed by the anchor tube.
 15. A method according toclaim 14, wherein the piston is fastened at the threaded rod andperforms an axial motion directed inwardly together with the threadedrod.
 16. A method according to claim 14, wherein prior to screwing thethreaded rod inwardly into the anchor tube, the threaded rod is onlypartially arranged in the interior space enclosed by the anchor tube,and during the transporting of the fixing agent out of the interiorspace enclosed by the anchor tube the threaded rod is essentiallyscrewed entirely into the interior space enclosed by the anchor space.